1. Field of the Invention
The present invention relates to an image processing system, more particularly to the image processing system for providing a desired image display for an object to be detected, on the basis of image information in a visible region corresponding to a field of view of a vehicle driver.
2. Description of the Related Arts
Recently, an image processing system is proposed for processing image information in a visible region in front of an automotive vehicle to form an image for various uses. According to Japanese Patent Laid-open Publication No. 6-215137, for example, it is proposed to provide an image processing system for detecting edge points in an image rapidly. This system is adapted to determine a scanning region by combining scanning line information such as a coordinate for beginning the scanning process and a coordinate for ending the scanning process, which are stored in a scanning table memory device.
In order to detect borders of a white line for defining the vehicle's path and extending ahead of the vehicle, theoretically it is sufficient to scan image data in a relatively narrow region to obtain edge points of the white line, because a region of a road wherein the white line is disposed is generally limited to a certain narrow region. However, a region for detecting an object is complex in shape, that scanning process could not be practiced in the system prior to the system proposed in the publication. According to the proposed system in the publication, therefore, the scanning region which is called as a "window" is determined in accordance with the combination of the scanning line information such as the coordinate for beginning the scanning process and the coordinate for ending the scanning process, which are stored in a scanning table memory device. According to the system, therefore, the scanning region, i.e., window, is not limited in shape, so that the detection of the white line can be made in a relatively short period by scanning only the minimum region.
The image processing system disclosed in the above publication is installed on the automotive vehicle, for example, and used to distinguish a boundary of a road in the driver's field of view when the vehicle travels on the road, i.e., along the white line of a lane. In this respect, by means of the window for encircling the white line, it is possible to increase a speed for detecting edges through a density in the image information, and prevent noise edges from being caused by foul or material on the road other than the white line to be detected, and improve the detection accuracy. The word of "edge" means a step-like variation in a density of an image, i.e., a place where brightness of the image varies to a great extent, so that the edge generally resides on an outline of an object.
In order to increase the speed for detecting the edges, it is preferable to form the window in a pattern corresponding to the shape of the object. In the above-described system, for example, it is preferable to form the window as narrow as possible to encircle only the white line of the lane. However, the lanes appeared on the image are of so many kinds that a large number of window patterns are to be provided in advance, and a window having an appropriate pattern is to be selected from the window patterns. Therefore, a large capacity of memory is necessitated, and it takes much time to select the appropriate pattern, so that the processing time might be extended.
Furthermore, if the object is varied in shape, for example the object is a curved lane which resides in a visible region in front of the vehicle, it is necessary to provide a plurality of windows for various patterns in advance in order to trace the curve of the lane properly and perform a necessary process immediately, so that a large capacity of memory is required.